Field of the Invention
The present invention relates to a method of manufacturing a laminated seamless belt and to the laminated seamless belt. More particularly, the laminated seamless belt is used suitably as an intermediate transfer belt of image-forming apparatuses such as a copying apparatus, a color copying apparatus, and the like.
In the image-forming apparatus, a toner image formed on a photoconductor is transferred to an intermediate transfer member, and then to a transfer object (mainly paper). A conductive seamless belt (hereinafter referred to as belt) is used as the intermediate transfer member. The intermediate transfer belt is tensionally mounted on a driving shaft and used for a long time. Thus the intermediate transfer belt is demanded to be durable. Further the intermediate transfer belt is charged and discharged repeatedly. Therefore the intermediate transfer belt is also demanded not to generate transfer nonuniformity by reducing the potential difference and the electric resistance value while maintaining a sufficient electric charge.
A conductive belt widely used has a single layer composed of a resin and an electroconductive filler consisting of carbon black or a metal oxide added to the resin.
In the single-layer belt, it is difficult to uniformly disperse the conductive agent in the resin in kneading the conductive agent into the resin. Therefore there is a large variation in the electric resistance value inside the formed belt. Consequently transfer nonuniformity is liable to occur when the toner image developed on the photoconductor is transferred to the belt. Hence it is difficult to obtain a preferable image.
In addition to the method of using the electroconductive filler, a method of adding an ionic-conductive agent to the resin is known. This method reduces the variation in the electric resistance value inside the belt. However, there is a fear that the ionic-conductive agent oozes out of the belt and stains the photoconductor.
To solve the above-described problem, the transfer belt having the base member serving as the conductive member and the dielectric layered thereon is known, as disclosed in Japanese Patent Application Laid-Open No. 53-87738 (patent document 1). The transfer belt having the laminated construction is superior to the single-layer transfer belt in the transferring performance thereof.
In the belt having the laminated construction disclosed in Japanese Patent Application Laid-Open No. 6-130830 (patent document 2), the outer layer consists of the dielectric layer made of thermoplastic resin having a tensile modulus of elasticity of not less than 8000 Kg/cm2, and the inner layer consists of the conductive layer made of the same thermoplastic resin as thermoplastic resin used for the outer layer.
In the belt having the laminated construction disclosed in the patent document 2, the tensile modulus of elasticity of the outer layer is not less than 8000 Kg/cm2. Thus when the driving shaft is successively rotated with the belt stretched thereon, the belt cracks at its edge and is hence liable to be torn. Thus the belt is not durable. When the electroconductive filler such as carbon black is used to impart conductivity to the belt, the electric resistance value inside the belt is liable to have variations and a stable image cannot be obtained. When the addition amount of the electroconductive filler is large, the obtained belt is frail. When the driving shaft is successively rotated with the belt stretched thereon in the case where polycarbonate that is a preferable thermoplastic resin is used for the belt, the edge of the belt is liable to be torn. Thus the belt is not durable. When a fluorine-containing polymer such as polyvinylidene fluoride (PVDF) is used for the belt, a corrosive gas may be generated when extrusion is carried out. Thus a molding machine having a special processing done thereon is required, which is disadvantageous in terms of the manufacturing cost. Olefin materials such as polyethylene, polypropylene, and the like are unfavorable in creep characteristic, has an elongation set, and a low durability for successive use.
Patent document 1: Japanese Patent Application Laid-Open No. 53-87738
Patent document 2: Japanese Patent Application Laid-Open No. 6-130830